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CLUSTER END-SYNC-CONTACTS · 7 ENTRIES · EARLIEST ENTRY 2017-02-27

Encrypted calendar and contact sync

These products provide end-to-end encrypted synchronization for calendars, contacts, and tasks across devices, with some offering self-hosting. The cluster's dated history is too thin to read a shape from—it predates the index or its members are undated. Among the traction leaders, three-device-caldav has the most stars (1), while SilentSuite and Agenda Tech have none.

Entry timeline

ENTRY TIMELINE

FEB 2017: 1DEC 2019: 1JAN 2024: 1OCT 2024: 1SEP 2026: 1OCT 2026: 2
FEB 2017OCT 2026

Each bar is the month a member carries, which is a creation date where the source published one and a crawl date otherwise. Nothing in the index was found before 11 August 2026, and coverage broadened sharply on 14–15 August, so a bar from then on reports how much we found that month, not how much was built; an earlier bar reports how far back a member's own source dated it — not how long we have been watching.

Members by activity

Activity signals, not revenue.

Build origin · 2 hand-coded · 5 unlabelled

Operator · 1 hobby · 6 open source

Two labels per entry, never collapsed into one: how it was built, and who stands behind it. Counted over the 7 listed below. Unlabelled means nothing has decided yet — not that the answer is small.

  1. 01SilentSuite - Secure Data Sync0★7 daysliveopen sourceSync service that keeps calendar, contacts, and tasks synchronized across devices with end-to-end encryption and self-hosting options.
  2. 02Agenda Tech0★11 daysliveopen sourceOffline calendar app that keeps events on-device with encrypted backups, recurring events, and reminders, requiring no account.
  3. 03three-device-caldav1★1 mo—hobbyPrivately hosted calendar synchronization tool that keeps personal calendars in sync between Windows, Android, and iOS devices.
  4. 04Tuta Calendar0★23 daysliveopen sourceEncrypted calendar app that schedules and manages events with end-to-end encryption and cross-device sync.
  5. 05EteSync - Secure Data Sync0★7 mostalelivehand-codedopen sourceSecure end-to-end encrypted sync for contacts, calendars, and tasks across devices.
  6. 06Infomaniak kSync0★8 mostaleliveopen sourceSync tool that keeps contacts and calendars in sync between cloud accounts and mobile devices while prioritizing user privacy.
  7. 07Fossify Calendar0★24 dayslivehand-codedopen sourceCalendar app for scheduling events, setting reminders, and syncing across accounts, designed to protect user privacy without ads or tracking.

Ranked by traction, highest first, and paged 20 at a time — this is a window on the cluster, never the whole of it. Ties are broken by a stable id so a product cannot appear on two pages or fall between them. Browse every cluster.